2.9. Transactions

Sometimes it is useful to be able to group messages
transfers - sent and/or received - on a session into atomic
grouping. This can be done be creating the session as
transactional. On a transactional session sent messages only
become available at the target address on commit. Likewise any
received and acknowledged messages are only discarded at their
source on commit
[8]
.

[8] Note that this currently is only true for
messages received using a reliable mode
e.g. at-least-once. Messages sent by a broker to a receiver in
unreliable receiver will be discarded immediately regardless of
transctionality.